Marijuana is the most commonly used illicit drug among adolescents;1-3 nearly half will have initiated use before high school graduation.17 Even recreational use is associated with negative behavioral, social and cognitive outcomes.2,8 Leading health organizations recommend screening and intervention for marijuana use during primary care visits11-14 and the majority of adolescents report wanting to discuss substance use with their provider.16 However, substance use screening in clinical visits is inconsistent;16 this gap has been attributed to physician discomfort, lack of training, uncertainty over management of positive screens limited time, or lack of reimbursement.22-24 NIDA has recognized the need for effective brief interventions for illicit drug use, including marijuana,9, 4 and the US Preventive Service Task Force has called for research to identify strategies for adolescent drug screening and tailored interventions.15 This study will address these needs by developing a marijuana screening and brief counseling intervention and testing it for use with adolescent users in pediatric primary care settings. The intervention is based on the Public Health Service 5As (Ask, Advise, Assess, Assist, Arrange) model,21,22 which has demonstrated success with adult tobacco smokers36 and has been adapted for other health behaviors.47-55 We are currently testing an adolescent adaptation of the 5As tobacco intervention in a NCI-funded national trial (R01 CA140576). Our specific aims are to (1) Develop a marijuana screening and brief counseling intervention for adolescents based on the 5As and (2) Pilot test the feasibility and acceptability of the 5As marijuana intervention in pediatric primary care practice. We will pilot the marijuana screening/brief counseling intervention for feasibility and acceptability in a sample of [10] practices from the American Academy of Pediatrics (AAP) Pediatric Research in Office Settings (PROS) practice-based research network. Intervention content will be drawn from content experts, current literature and themes gathered from focus groups and in-depth interviews with clinicians, adolescents and parents. The control arm of this study will use a comparable-burden intervention focused on social media use; adapted from our ongoing R01. Up to [80] clinicians, 100 parents and [1020] adolescents will participate in the three phases of this study. We will conduct follow-up interviews with a sample of adolescent marijuana users and non-users [enrolled at intervention sites] to assess physician-delivery of the intervention and any change in use, attitude or behavioral intentions towards marijuana since their clinical visit. Findings will inform the development of a future large-scale trial of adolescent marijuana use, screening and cessation counseling in pediatric primary care. Our long-term goal is to improve clinical preventive services for adolescent marijuana cessation. Conducting this work within the AAP PROS network will lead to rapid dissemination of effective interventions.